The present invention relates to apparatus and methods for three-dimensional (hereinafter xe2x80x9c3Dxe2x80x9d) surface reconstruction.
State of the art computational methods relevant to 3D surface reconstructions are described in the following articles:
xe2x80x9cTrilinearity of three perspective views and its associated tensorxe2x80x9d, Shashua and Werman, ICCV (International Conference on Computer Vision) ""95, June 1995;
xe2x80x9cRelative affine structure: canonical model for 3D from 2D geometry and applicationsxe2x80x9d, Shashua and Navab, IEEE Transactions on PAMI, 18(9), September 1996; and
xe2x80x9cAlgebraic functions for recognitionxe2x80x9d, A. Shashua, IEEE Transactions on PAMI, 17(8), August 1995.
A survey of state of the art methods for non-contact measuring is Tatterson, K. G., xe2x80x9cLaser measurement finds its marketsxe2x80x9d, Photonics Spectra, October 1996.
The disclosures of all publications mentioned in the specification and of the publications cited therein and of Israeli Patent Application 113496 and U.S. patent applications Ser. No. 08/497,224 (whose disclosure corresponds to International Publication No. WO 96/34365, published Oct. 31, 1996) and No. 08/787,345 (whose disclosure corresponds to U.S. Pat. No. 5,598,515) are hereby incorporated by reference.
Speckle metrology and interferometry are known for various applications. In speckle metrology, speckles are generated on an object sought to be inspected or measured. The speckles thus generated on the object of interest are highly dependent on the angular relationship between each surface of the object of interest and a laser or other light source used to generated the speckles thereon. Speckle metrology methods are described in Speckle Metrology, Rajpal S. Sirohi (Ed.), Marcel Dekker, Inc., 1993.
The present invention seeks to provide a novel and highly efficient 3D surface geometry reconstruction system.
There is thus provided in accordance with a preferred embodiment of the present invention 3D surface geometry reconstruction system for reconstructing the surface geometry of an object to a given degree of precision, the system including:
a three-view optic head operative to generate at least three views of at least a portion of the object;
a mechanical manipulator operative to vary the relative orientation of the object and the optic head, at a precision less than the given degree of precision, from a first relative orientation in which a first portion of the object is visible to at least one second relative orientation in which a second portion of the object, which overlaps the first portion, is visible;
a local 3D surface geometry reconstruction unit operative to reconstruct the surface geometry of the first and second portions of the object, based on at least two of three views of the first and second portions generated by the optic head; and
a surface geometry stitching unit operative to determine the relative locations of the first and second portions of the objects.
In accordance with a preferred embodiment of the present invention, the mechanical manipulator includes an object manipulator operative to move the object.
Preferably, the mechanical manipulator includes an optic head manipulator operative to move the optic head.
In accordance with a preferred embodiment of the present invention, the three views generated by the optic head include two views on which 3D surface geometry reconstruction is based and a third view from which a tensor is computed which represents the internal orientation of each of the three views and the relative orientation of the three views.
Preferably, the object includes:
a first section of the object seen in one of the three views;
a second section of the object seen in another of the three views; and
an overlap section of the object which is included in the first section and the second section; and
wherein the 3D surface geometry reconstruction unit includes an overlap section analyzer operative to analyze texture of the overlap section.
In accordance with a preferred embodiment of the present invention, the surface geometry stitching unit includes an overlap texture analyzer operative to analyze texture of a section of the second portion which overlaps the first portion, thereby to determine the relative locations of the first and second portions.
The texture may include the surface texture of the object and or texture applied to the object by a texturing process.
Preferably, the texture does not vary as a result of variation in the relative orientation of the object and the optic head.
In accordance with a preferred embodiment of the present invention, the texturing process includes an optical process for superimposing a pattern onto the object. Preferably, the optical process includes projecting a speckle pattern onto the object.
Preferably, the texture is projected onto the object.
In accordance with a preferred embodiment of the invention, the texture is a speckle pattern projected onto the object.
Preferably, the system includes a plurality of speckle generators each projecting a random speckle pattern onto the object.
Each speckle generator preferably comprises a diffuser on which a speckle pattern is generated and through which light is projected to project the speckle pattern from the diffuser onto a portion of the object.
Preferably, each speckle generator includes a laser diode which directs laser light via a lens onto said diffuser.
In accordance with a preferred embodiment of the invention, the diffuser is a holographic diffuser.
There is additionally provided in accordance with a preferred embodiment of the present invention a three dimensional imaging system comprising:
an imaging head;
positioning apparatus for varying the relative position between an object to be imaged and
the imaging head;
at least one speckle generator projecting a speckle pattern onto the object, which speckle pattern is fixed with respect to the object and is invariant with the angle from which it is viewed by the imaging head; and
an image combiner for combining multiple images of the object as seen by the imaging head at different relative positions with respect thereto, by matching portions of the speckle pattern on various ones of the multiple images.
There is also provided in accordance with a preferred embodiment of the present invention a 3D surface geometry reconstruction system for reconstructing the surface geometry of an object, the system including:
an optical head; and
a mechanical manipulator operative to vary the relative orientation of the object and the optic head with at least five degrees of freedom and including:
an object manipulator operative to move the object; and
an optic head manipulator operative to move the optic head;
a 3D surface geometry reconstruction unit operative to reconstruct the surface geometry of the object by analyzing images of at least portions of the object generated by the optic head.
Preferably, the mechanical manipulator provides a plurality of relative orientations of the object and the optical head such that the entire surface of the object is imaged by the optical head and wherein the surface geometry stitching unit is operative to reconstruct the entire surface of the object.
There is additionally provided in accordance with a preferred embodiment of the present invention a 3D surface geometry reconstruction system for reconstructing the surface geometry of an object, the system including:
a surface location computation unit operative to compute a multiplicity of locations falling on the surface of the object;
There is additionally provided in accordance with a preferred embodiment of the present invention a 3D surface geometry reconstruction method for reconstructing the 3D surface geometry of an object, the method including:
manually varying the relative orientation of the object and an optic head and generating a plurality of images of at least portions of the object for a corresponding plurality of relative optical head/object orientations; and
reconstructing the 3D surface geometry of the object by analyzing the plurality of images.
A particular advantage of a preferred embodiment of the system shown and described herein is that the system can accurately reconstruct the 3D surface geometry of an object, without precise mechanical elements which, in conventional systems, are used to provide high precision scanning motion over the object""s surface. The system is particularly suited for reconstruction of objects whose size and/or shape is such that only a portion thereof can be captured by a stationary imaging device,
Another advantage of a preferred embodiment of the system shown and described herein is that entirely automatic surface reconstruction may be provided without any human intervention whatever.
Another advantage of a preferred embodiment of the system shown and described herein is that a particularly high density of reconstructed surface points is provided.
The robot of the present invention preferably has 6 degrees of freedom, including a vertical degree of freedom for manipulating the object and a vertical degree of freedom for manipulating the optic head. Alternatively, only one of these vertical degrees of freedom may be provided.